1. Field of the Invention
The present invention generally relates to sensor units, and more particularly to a sensor unit composed of a permanent magnet, a spherical body formed of a magnetic material, and a magnetic sensor and used for inclination and acceleration measurement.
The sensor units are employed in automobiles, game controllers, and projectors. The sensor units are preferably small in size and easy to incorporate into apparatuses.
2. Description of the Related Art
FIG. 1 is a diagram showing a sensor unit 10 disclosed in Japanese Laid-Open Patent Application No. 2000-180160. The sensor unit 10 includes a spherical body 13 formed of a magnetic material and supported on a spherically concave partition wall 12 in the center of a container 11. The sensor unit 10 also has a permanent magnet 15 fixed to a bottom plate 14 of the container 11 and a Hall element 17 fixed to the bottom surface of a top plate 16 of the container 11. The permanent magnet 15 generates a first magnetic field indicated by lines of magnetic force 18. The magnetic spherical body 13 is magnetized by the first magnetic field so as to generate a second magnetic field indicated by lines of magnetic force 19. The second magnetic field affects the Hall element 17 so that the Hall element 17 outputs voltage.
The sensor unit 10 has a height ho indicated by an arrow in FIG. 1. In the sensor unit 10, in the direction of the height thereof, the magnetic spherical body 13 is positioned in the center, the permanent magnet 15 is positioned below the magnetic spherical body 13, and the Hall element 17 is positioned above the magnetic spherical body 13.
The sensor unit 10, for instance, is mounted in an electronic apparatus such as a vehicle or a projector. When the apparatus is inclined, the magnetic spherical body 13 rolls on the partition wall 12 so as to change position with respect to the permanent magnet 15 and the Hall element 17. Thereby, a change is effected in the second magnetic field affecting the Hall element 17 so as to vary the output voltage thereof. The angle and direction of inclination of the electronic apparatus is detected based on the variation in the output voltage of the Hall element 17.
In the above-described sensor unit 10, especially, the Hall element 17 is provided above the magnetic spherical body 13. Therefore, a part above the magnetic spherical body 13 takes up much space so that the height ho of the sensor unit 10 is required to be large, thereby making it difficult to downsize the sensor unit 10.
Further, in a normal sensor unit, a Hall element is mounted on a printed board, being electrically connected with pads on the printed board. However, in the sensor unit 10, the Hall element 17 is provided in an upper part of the sensor unit 10, thus complicating a route of extension of interconnection lines from the Hall element 17.
Accordingly, it is a general object of the present invention to provide a sensor unit in which the above-described disadvantage is eliminated.
A more specific object of the present invention is to provide a sensor unit reduced in size and assembled with ease.
Another more specific object of the present invention is to provide a sensor unit performing detection with increased accuracy.
The above objects of the present invention are achieved by a sensor unit including a support body having a concave surface, a spherical body formed of a magnetic material and placed on the concave surface of the support body so as to roll freely thereon, a permanent magnet producing a magnetic field affecting the magnetic spherical body, and a magnetic sensor detecting a change in the magnetic field caused by the movement of the magnetic spherical body, wherein the magnetic spherical body and the permanent magnet are provided to oppose each other with a given distance therebetween in a vertical direction, the magnetic sensor is provided between the magnetic spherical body and the permanent magnet, and an output is produced in accordance with the detection by the magnetic sensor.
According to the above-described sensor unit, the magnetic sensor is provided by using a space between the magnetic spherical body and the permanent magnet provided to oppose each other with the given distance therebetween. Therefore, no additional space is required for providing the magnetic sensor. Accordingly, the sensor unit is downsized with a reduced height.
The above objects of the present invention are also achieved by a sensor unit including a support body having a concave surface, a spherical body formed of a magnetic material and placed on the concave surface of the support body so as to roll freely thereon, a permanent magnet producing a magnetic field affecting the magnetic spherical body, a magnetic sensor detecting a change in the magnetic field caused by the movement of the magnetic spherical body, and a printed board having first and second opposing surfaces, wherein the magnetic sensor is provided to the first surface of the printed board, the support body is fixed to the first surface of the printed board, the permanent magnet is fixed to the second surface of the printed board, and an output is produced in accordance with the detection by the magnetic sensor.
According to the above-described sensor unit, the magnetic sensor is provided by using a space between the magnetic spherical body and the permanent magnet provided to oppose each other with a given distance therebetween. Therefore, no additional space is required for providing the magnetic sensor. Accordingly, the sensor unit is downsized with a reduced height.
Additionally, the above-described sensor unit may include a Hall element for temperature compensation, the Hall element being provided to a surface of the permanent magnet on a side opposite to the printed board.
Thereby, temperature compensation is provided to the magnetic sensor and the permanent magnet, thus increasing detection accuracy.
The above objects of the present invention are also achieved by a sensor unit including a case, a printed board having a magnetic sensor provided thereto, a hanging member including a permanent magnet producing a magnetic field, and a hanging and support mechanism that hangs and supports the hanging member in the case so that the hanging member is allowed to swing while being restricted in displacement in a vertical direction, wherein the magnetic sensor detects a change in the magnetic field caused by a movement of the permanent magnet due to the displacement of the hanging member so that an output is produced in accordance with the detection by the magnetic sensor.
According to the above-described sensor unit, the hanging and support mechanism restricts displacement of the hanging member in the vertical direction so that no change is caused in the output even when vibration or impact is exerted on the sensor unit in the vertical direction. Therefore, the sensor unit has good impact resistance, thus assuring good detection accuracy.
The above objects of the present invention are also achieved by a sensor unit including a case, a printed board having a magnetic sensor provided thereto, a balancing assembly having a permanent magnet producing a magnetic field, and a pivot support mechanism that supports the balancing assembly in the case so that the balancing assembly is allowed to swing, wherein the magnetic sensor detects a change in the magnetic field caused by a movement of the permanent magnet due to the displacement of the balancing assembly with respect to the printed board so that an output is produced in accordance with the detection by the magnetic sensor.
The above-described sensor unit is reduced in size and easy to assemble.
Additionally, the above-described sensor unit may include a detection switch provided in the case so as to oppose the top part of the balancing assembly, and the detection switch may detect an upward displacement of the balancing assembly to make the output of the sensor unit invalid.
The detection accuracy of the sensor unit decreases with the balancing assembly being in an upward displaced state. Therefore, the detection switch makes less accurate data invalid so that only highly accurate data is output from the sensor unit.
Additionally, the above-described sensor unit may include a part that affects the permanent magnet of the balancing assembly so that a flotation force is magnetically exerted on the balancing assembly.
Since the flotation force is exerted on the balancing assembly, frictional force is reduced between the balancing assembly and the pivot support mechanism, thus increasing the swing sensitivity of the balancing assembly.
The above objects of the present invention are also achieved by a sensor unit including a swing part including a swingable magnet, electromagnetic transducers detecting magnetism of the magnet, and a magnetic shield member shutting off a magnetic effect on the magnet.
According to the above-described sensor unit, the magnet is magnetically shielded so that magnetic interaction between the magnet and an external magnetic material can be reduced. Therefore, the sensor unit can perform detection with increased accuracy.
The above objects of the present invention are also achieved by a sensor unit including a swing part including a swingable magnet, electromagnetic transducers detecting magnetism of the magnet, a case having a spherical internal surface substantially centered on a pivot center of the swing part and accommodating the swing part, and a magnetic shield member provided to the spherical internal surface of the case.
According to the above-described sensor unit, the magnetic material is provided to the spherical internal surface of the case so that the magnet can be magnetically shielded with a constant distance being maintained between the magnet and the magnetic material.
The above objects of the present invention are further achieved by a sensor unit including a swing part including a swingable magnet, electromagnetic transducers detecting magnetism of the magnet, a case accommodating the swing part, and an elastic force application part applying an elastic force to the swing part.
According to the above-described sensor unit, the elastic force is applied to the swing part so that displacement of the swing part is reduced with respect to, for instance, acceleration, thus enlarging the detectable range of acceleration.